Year	% of expense
1997	43.778180532827314
1998	42.03421389503084
1999	39.115554336101
2000	44.275296231906154
2001	46.60150002936801
2002	38.40970301066299
2003	36.90702218710451
2004	36.99194710330269
2005	38.125394920518175
2006	41.05536616781536
2007	41.67006828725856
2008	43.203632521686075
2009	44.556529977025455
2010	41.982176179904314
2011	44.93597320875457
2012	45.62893509392048
2013	46.013023567144984
2014	45.63315065419537
2015	45.346134707518495
2016	44.59260401284718
2017	43.923391812865496
2018	44.45429058480438
2019	44.597069245995996
2020	48.02518193705828
2021	48.29770585596714
2022	45.909270640538516